There has been proposed a variable magnification optical system that is suitable to be used for a photographic camera, an electronic still camera, a video camera and the like. For example, please refer to a Japanese Patent application Laid-Open Gazette No. H4-293007. However, a variable magnification optical system as disclosed in the Japanese Patent application Laid-Open Gazette No. H4-293007 is not intended to make a focusing group light in weight sufficiently and is not suitable for attain high speed focusing operation.